WO1992015901A1

WO1992015901A1 - Optical transmitter made of graded index type plastic, and method of producing the same

Info

Publication number: WO1992015901A1
Application number: PCT/JP1992/000210
Authority: WO
Inventors: Yoshihiro Uozu; Kouzou Mise; Nobuhiko Toyoda; Yoshihiko Hoshide
Original assignee: Mitsubishi Rayon Co., Ltd.
Priority date: 1991-03-01
Filing date: 1992-02-26
Publication date: 1992-09-17
Also published as: DE69213866D1; TW255016B; DE69213866T2; US5287222A; KR930700857A; KR100260568B1; EP0527239B1; JP3301760B2; EP0527239A4; EP0527239A1

Abstract

An optical transmitter having a radius (ro?) of 0.45 0.1 mm and made of a graded index plastic, wherein a refractive index distribution within the range of at least 0.2 ro? to 0.8 ro? exhibits a distribution approximate to an optimum quadratic curve which makes a mode dispersion minimum. It has a demodulation transfer factor, which represents resolution, of at least 60 %, and is suitable for image transfer in a copying machine, a facsimile, an image sensor, etc. The present invention relates also to a method of producing an optical transmitter obtained by removing a predetermined amount of the outer periphery of a graded index type optical transmitter preform.

Description

Specification

Graded-index blast optical transmitter and its manufacturing method

Technical field

The present invention relates to a graded index (type) that can be usefully used as various optical transmission lines such as an optical converging optical fiber, an optical converging rod lens, and an optical sensor. The present invention relates to an optical transmitter made of blast and a method of manufacturing the same, and more particularly to an optical transmitter capable of transmitting a high-quality image with high resolution and little chromatic aberration, and a method of manufacturing the same.

Background technology

2. Description of the Related Art In recent years, rod-shaped optical transmitters have been increasingly used for image transmission in facsimiles, copiers, image sensors, and the like. Such an optical transmission medium enables high-quality image transmission with high resolution and little chromatic aberration, and a manufacturing method in which the quality variation between the optical transmission bodies is small even when mass-produced can be adopted. This was desired.

In such an optical transmission body for image transmission, the refractive index is continuously reduced from the center to the outer periphery in the cross section of the optical transmission body, and the distribution has a mountain-shaped inclination. The attached GI optical transmitter is used. Such GI-type optical transmission suspensions are disclosed in Japanese Patent Publication No. 47-816, Japanese Patent Publication No. 47-28059, EP Publication No. 2008-159, etc. .

The GI type optical transmitter disclosed in Japanese Patent Publication No. 47-1816 was made of glass and was made by the ion exchange method. Therefore, it is difficult to produce products with the same shape and the same performance between different lots because of low productivity, especially rods of the same length with a certain total conjugate length. It is difficult to make the same lens with the same performance between different rods. As a result, the length of the GI type optical transmitter with the same performance is not uniform, and the handling is difficult. There was a drawback that it became difficult.

The GI-type plastic optical transmitter disclosed in JP-B-47-28059 is a mixture of two or more transparent polymers having different refractive indices and different solubilities in a specific solvent. A rod-shaped or fiber-shaped shaped article is immersed in the above-mentioned solvent, and the mixing ratio of the above-mentioned polymer is changed from the surface to the center of the shaped article. It is made by doing. By this method, a plastic GI optical transmitter can be produced for the time being, but a mixture of two or more polymers having different refractive indices tends to cause a disorder in the refractive index distribution. It is difficult to make the refractive index distribution from the part toward the outer periphery follow the optimum distribution curve. In addition, the transparency of the optical transmitter is reduced, and light scattering is likely to occur. The characteristics of the GI type optical transmitter are not sufficient, and the application development thereof is not progressing.

EP Publication No. 0 218 159 discloses that at least one kind of thermoplastic polymer (A) is compatible with the polymer (A) when polymerized, and the polymer (A) The monomer (B) is volatilized from the surface of the molded article obtained by molding a homogeneous mixture of the monomer (B), which is a polymer having a different refractive index from that of the polymer (B), into a rod shape. This gives a continuous concentration distribution of the monomer (B) from the surface of the molded article to the center thereof, and then polymerizes the unpolymerized monomer in the molded article. Thus, a method of making a GI type plastic optical transmission medium is shown.

Ideally, the refractive index distribution curve of a GI optical transmission medium should have a quadratic distribution curve expressed by the following equation (3), and such a curve is indicated by the curve indicated by A in Fig. 2. It is said that

N = N 0 (1-ar ² ) (3) According to the study of the present inventors, the interface acoustic interference microscopy of the GI type optical transmission body made by the above-mentioned conventional method was performed. The refractive index distribution curve measured with a microscope is shown at B in Fig. 2 and is 0.5 r from the center in the radial direction. ~ 0.75 r. (In the same figure, the range from c to d, and e indicates the outer periphery). The refractive index distribution curve has a shape relatively close to the optimal curve shown by equation (3). The outer and inner refractive index distributions have shapes that deviate significantly from the optimal curve.

Observation of the lattice pattern using an optical transmitter having a refractive index distribution curve that almost exactly follows the optimal curve defined by equation (3) yields a normal lattice image as shown in Fig. 3 (a). However, as shown in Fig. 2B above, when a lattice image is observed using an optical transmission body whose refractive index distribution deviates from the ideal refractive index distribution, Fig. 3 (b) Or, as shown in (c), a large and distorted lattice. Only images can be obtained, and accurate image transmission cannot be performed. Such an optical transmission The body resolution can be indicated by a modulation 'transfer' factor (hereinafter referred to as MTF). First, as shown in FIG. 4, the light of the light source (42) is adjusted by the lens (43), as shown in FIG. 4, to calculate the MTF values of the optical transmitter of the prior art and the optical transmitter of the present invention. The light passing through the grating (45) having a lattice constant of 4 (Limpano mm) is applied to the GI-type optical transmitter (41), and the lattice image passing through the optical transmitter is applied to the CCD sensor (46). And the maximum value i ». X and the minimum value i of the measured light quantity were measured as shown in FIG. 5 and determined by the following equation (4). The lattice constant here rather each shown in the lattice of Figure 4, a set of combinations of white line and black line 1 la Lee amps and to what the width of La Lee amps force ^s lmm this It is a value that indicates whether or not the line is provided.When this line pair has 4 lines Zm m, it is displayed as 4 line pairs mm

MTF (¾) = {(im, xi »ln) / (im.x + im in)} X 100 (4) has a refractive index distribution that almost exactly follows the optimal curve defined by the above equation (3) GI-type plastic optical transmitters have not been developed yet.

Prior to the present invention, the present inventors used a monochromatic light source such as an LED, and had a resolution high enough to be usefully used as an optical transmitter for a facsimile image sensor and chromatic aberration. We studied with the aim of obtaining an optical transmission body made of GI type plastic with a small radius r. Is within a range of 0.5 ± 0.1 mm, and is at least 0.25 r from the central shaft to the outer peripheral surface. ~ 0.70 r. Is defined by the above formula (3). A refractive index distribution approximating the refractive index distribution curve to be obtained is provided, and a grid image of 4 line Pano mm is formed on the CCD line sensor through the light transmitting body and measured. were measured and the maximum light intensity value im and the minimum light intensity value i »i _n, GI type Burasuchi characterized that you formula MTF calculated in (4) is provided with the not cormorants characteristic is 4 0% or more An optical transmission body made by Nippon Kogyo Co., Ltd. was proposed in Japanese Patent Application No. 113706/1996.

The refractive index distribution in the radial direction of the GI optical transmission body achieved by the present invention is as shown in [[] of FIG. 1 and is a curve [I] that follows the optimal curve of equation (3). The number of parts that correspond to the number increases, and when image transmission is actually performed with this optical transmitter, its performance is higher than the image transmission characteristics of a conventionally developed optical transmitter made of plastic. Has been significantly improved.

However, the radius from the periphery of the GI-type optical transmission body, particularly from the center of the optical transmission body, is r. 0.70 r. Therefore, the refractive index at the outer periphery deviates greatly from the optimal curve of Equation (3), and the periphery of the image transmitted by such an optical transmission medium is distorted or blurred. However, it is not always satisfactory as an optical transmitter for transmitting high-quality images. 0.7 r to eliminate such inconveniences. A method of making the outer peripheral area blacker has been studied, and although some effects have been obtained, the image transmission effect of the entire optical transmission body is reduced by blackening accordingly. There is a problem of doing so and it is not enough.

Disclosure of the invention

Therefore, the present inventors assumed the bending as shown in [I] in FIG. A GI-type plastic optical transmission medium with a refractive index distribution is made to remove the areas C to D (F) from the areas C to E shown in Fig. 1. As a result, the present inventors have found that a GI-type optical transmitter can be obtained in which the above-mentioned difficulties have been remarkably improved, and the present invention has been completed.

The gist of the present invention is the radius r. Is a GI plastic optical transmission body having a circular cross-section within a range of 0.45 mm and 0.1 mm, and a small amount of the light transmission body extends from the central axis to the outer peripheral surface of the optical transmission body. Especially 0.25 r. ~ 0.8 ro, preferably 0.225 r. ~ 0.85 r. The GI type plastic optical transmission body is characterized in that the refractive index distribution in the range of (1) has an approximate refractive index distribution to the refractive index distribution curve defined by the following equation (1).

n (r) = n ₀ {l- (gV2) r ² } (1)

(In the above formula, η is the refractive index of the central axis of the optical transmission member, and is an arbitrary value within the range of 1.5 ± 0.1. Η (r) is the optical transmission member. , The refractive index at a position at a distance r from the center axis of the optical transmission member to the outer peripheral direction, g represents the refractive index distribution constant of the optical transmission body, and is a value of 0.3 to 0.7, and r is the light transmission coefficient. Indicates the distance from the center axis of the transmission body toward the outer periphery.)

Furthermore, the radius L. At least 0.25 from the central axis to the outer peripheral surface of the GI-type plastic optical transmission body preform having a circular cross section within the range of 0.5 ± 0.1 mm. L. ~ 0.7 L. The feature is to remove the outer periphery of the optical transmitter preform having a refractive index distribution whose refractive index distribution approximates the refractive index distribution curve defined by the following equation (2). The method of manufacturing the GI-type plastic optical transmission body described above.

n (L) = No {l- (g 2/2) L 2} (2)

(In the above formula, N. is a refractive index of the central axis portion of the optical transmission medium, and is an arbitrary value within a range of 1.5 ± 0.1. ) Indicates the refractive index at a position at a distance L from the central axis of the optical transmission medium toward the outer periphery, and g indicates the refractive index distribution constant of the optical transmission medium. , 0.3 to 0.7, and L indicates the distance from the central axis of the optical transmission body toward the outer periphery.)

The GI-type plastic optical transmission body of the present invention has at least 0.25r from the central axis toward the outer peripheral surface. ~ 0.8 r. , Preferably 0 · 25 Γ. ~ 0 · 85 Γ. Since the refractive index distribution in the range of has a refractive index distribution approximating the optimal curve of the refractive index distribution defined by the above equation (1), a grid image of 4 line pairs mm is transmitted through the optical transmission body to the CCD line. The maximum light intensity value i «· _χ and the minimum light intensity value i _η measured by imaging on the sensor are measured, and the characteristic that the MTF calculated by the above equation (4) is 60% or more is provided. this and force ⁵ can and Do Ri, compared to the GI optical transmission article have been conventionally developed can and this performing quality image transmission, becomes excellent light transmission member, especially no image Bo Ke peripheral portion.

The optical transmitter of the present invention has a radius r. Has a circular cross-section in the range of 0.45 ± 0.1 mm, so that at least r = 0.25r. ~ 0.8 r. Within this range, the refractive index distribution can be made the optimum distribution. Radius r. Is in the above range For larger values, 0.25 r. ~ 0.8 r. It is difficult to satisfy Equation (1) in the range of. On the other hand, the radius r

If 0 is less than the above lower limit, the handleability will be inferior.

In the present invention, "approximately J" to the optimum curve of the refractive index distribution means that the refractive index is within ± 0.0001 from the optimum curved force in the specified range.

In the above equation (1), the refractive index n of the central axis portion. If it is outside the above specified range, it will be difficult to increase the MTF to 60% or more. If the refractive index distribution constant g is larger than the above specified range, the conjugation length becomes too short and it becomes difficult to set a distance for operation. Conversely, if it is too small, the conjugate length will be long, and it will be difficult to reduce the size of a facsimile medium-scanner or the like incorporating an optical transmitter.

Hereinafter, the GI optical transmitter of the present invention will be further described together with the method of manufacturing the GI optical transmitter of the present invention.

The optical transmitter according to the present invention produces an optical transmitter preform having a specific performance, and then removes the outer periphery of the preform by, for example, physically peeling off the outer periphery. It is obtained by

The pli off O over arm is depends refractive index after curing each other, the viscosity at uncured state is prepared 3 or more uncured liquid substance is 1 0 ³ to 1 0 ⁸ Boi's, the non The cured liquid material is supplied to a multilayer composite spun nozzle, for example, so that the refractive index decreases gradually from the center to the outer peripheral surface, and is concentrically laminated. Trandoff Eye When the refractive index after curing of each layer and the thickness of the layer are made into a strand fin, the center position of each layer is the center from the strand fiber. When the distance from the axis is plotted on the abscissa and the refractive index of each eyebrow is plotted on the ordinate, the equation (2) should be made to match, and then this strand fiber An uncured strand fiber is applied while inter-diffusion treatment of the material between adjacent layers is performed or after inter-diffusion treatment so that the refractive index distribution between the layers becomes a continuous refractive index distribution. Can be obtained by hardening.

When only two types of uncured liquid materials having different refractive indices are used, 0.25 L from the center of the foam. ~ 0.7 L. Within this range, it is difficult to approximate the refractive index distribution to the quadratic curve of equation (2). Therefore, it is preferable that there are three or more uncured liquid materials having different refractive indexes from each other. Conversely, even if there are many types, it is difficult to adjust the refractive index distribution, and after all, it is more preferably 3 to 7 types, and even more preferably 3 to 5 types.

Viscosity Yes displacement of the uncured liquid material used in the present invention also have ¹ 0 ³ ~ 1 0 β and is not to like this in the range of Boi's. The viscosity tends to the formation of 1 0 ³ Ri by Boi's small and Itosetsu Re filamentous product frequently during shaping becomes difficult. If the viscosity is greater than 10 ^β- voids, the shaping operability will be poor, making it difficult to arrange each layer concentrically, and shaping with large unevenness in thickness. It becomes easy to become things.

The uncured liquid substance used in the present invention is a substance that can be cured, that is, polymerizable and cross-linkable, and may be a radically polymerizable vinyl monomer or the same. A composition comprising a monomer and a polymer soluble in the monomer can be used.

Specific examples of the radically polymerizable vinyl monomer that can be used include methyl methacrylate (η = 1.49), styrene (η = 1.59), and chlorstyrene. (Η = 1.61), butyl acetate (η-1.47), 2,2,3,3-tetrafluoropropyl (meta) acrylate, 2,2,3 3,4,4,5,5-octafluoropentyl (meta) acrylate, 2,2,3,4,4,4-hexafluorobutyl (meta) acrylate, 2 Fluorinated alkyl (meth) acrylates (η-1.3.37; L.44), 2,2,2-Trifluoroethyl (meta) acrylate, refractive index 1.43 ~: I.62 (meta) acrylates such as ethyl (meta) acrylate, phenyl (meta) acrylate, benzyl (benzyl) Meta) Acrylate, Hydroxia Alkyl (meth) acrylate, alkylene glycol (meta) acrylate, trimethylol propane (meta) acrylate, trimethylolprono \ Entry (meta) acrylate, pentaerythritol, tri or tetra (meta) acrylate, jigly serentiator (meta) Acrylate, dipentaerythrylhexa (meta) acrylate and diethylene glycol bisulfate carbonate, fluorinated alkylene glycol Meta) Accelerate rate.

In order to adjust the viscosity of these uncured liquid substances and to have a refractive index distribution from the center to the outer periphery of the obtained strand fiber-like shaped product, the above-mentioned uncured liquid is used. Substance is on It is preferably composed of a vinyl monomer as described above, and a polymer and a force soluble in the butyl monomer. The polymer used here must have good compatibility with the polymer formed from the above-mentioned radical polymerizable polymer monomer power, and such a polymer is required. Examples of the polymer include polymethyl methacrylate (n = l.49) and volume methacrylate cholesterol-based copolymer (n = l.0447). -1.50), poly (4-methylpentene) -11 (n = l.46), ethylene / bulcopolymer acetate (n = l.46-); 50), Polycarbonate (n = l.50 ~: I.57), Polywitzinivinylidene (n = l.42), Vinylidene fluoride La Fluoroethylene copolymer (n = l.42 ~: I.46), vinylidene fluoride tetrafluoroethylene / hexafluorobrovirene copolymer (n = l.40 ~; I.46), PO Etc. off Uz alkyl (meth) § click Re-les-over door port Li Ma chromatography, and the like.

It is preferable to use polymers having the same refractive index for each layer in order to adjust the viscosity, since a blast optical transmitter having a continuous refractive index distribution from the center toward the surface can be easily obtained. In particular, polymer methyl acrylate is excellent in transparency and has a high refractive index of itself, so that it is suitable as a polymer used in producing the GI type optical transmission body of the present invention. It is.

In order to harden the strand fiber formed from the uncured material, it is preferable to add a heat curing catalyst and a photo-curing catalyst to the uncured material. No. That is, the thermosetting catalyst and Then, the strand fiber containing the photocuring catalyst is heated or heat-treated, or irradiated with light, preferably ultraviolet light, from the surroundings.

As the thermosetting catalyst, an ordinary peroxyside catalyst is used. Benzofuenone, benzoin alkyl ether, 4'-isoprobiyl-1 2 -hydroxyl 2 -methyl-ropiophenone, light-curing catalysts as light curing catalysts Phenyl ketone, benzyl methyl ketone, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthonone compound, benzophenone compound, benzophenone compound, 4-dimethylamino Ethyl benzoate, 41-dimethylaminoisoamyl benzoate, N-methyljetanolamine, triethylamine, and the like.

Light sources used for photopolymerization include carbon arc lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, chemical lamps, and xenon lamps that emit light with a wavelength of 150 to 600 nm. , Laser light and the like.

The radius of the rod of the optical transmission medium must be in the range of 0.5 ± 0 · lmm, and if the radius is larger than this range, the radius of the bridge becomes larger. 0.25 L of home rod. ~ 0.70 L. It is difficult to obtain a refractive index distribution that is close to the highest expression represented by the expression (2) within the range described above, and the preform for manufacturing a high-resolution GI optical transmission body, which is the object of the present invention, is obtained. It becomes difficult to make a game.

In the production of preform rods, the composition of each uncured substance (monomer polymer ratio, refractive index, etc.) The refractive index of the preform rod can be set to 0.2 by appropriately combining the output ratio, the discharge nozzle temperature, the temperature at the time of mutual diffusion, time, light or heat curing (polymerization) conditions, and the like. 5 L. ~ 0.70 L. It can be approximated to the quadratic equation of equation (2) within the range of.

The method of removing the outer periphery of the optical transmitter preform is as follows: (1) The outer periphery of the optical transmitter preform is swollen with a solvent and a predetermined size is obtained in that state. (2) a method of cutting the outer periphery of the optical transmission body preform with a cutting tool, (3) a method of cutting the swollen portion through a hole having a hole diameter of (3) Examples of the method include immersing the reform in an alkaline solution or the like, and dissolving and removing the outer peripheral portion.

The method of swelling the optical transmission medium of (1) with a solvent is to put the plastic optical transmission medium in a solvent capable of dissolving the plastic. After immersion and swelling within a predetermined range, the swelled part is cut through a circular hole with a predetermined diameter, and the type of solvent used, immersion time in the solvent, swelling Depending on the temperature and the size of the circular hole, the cutting width can be adjusted.

Solvents for dissolving the plastic for optical transmission medium such as black mouth form, methylene chloride, carbon tetrachloride, methyl ethyl ketone, acetate, and ethyl acetate. Can be mentioned.

The method of shaving the outer periphery of the optical transmission body foam with the cutter of (2) can be performed, for example, by a method as shown in the perspective view of the cutter in FIG. it can. In the figure, (10) is This is an optical transmission body form, and (11) is a GI type optical transmission body having high resolution characteristics of the present invention. The number of cutting teeth (22) may be one, but it is preferable to use them in combination. A plurality of cutting teeth are attached to the rotating body (21) and the driving source (24) is used. By rotating, the outer circumference of the optical transmission medium preform that passes through the hole at the center of rotation is efficiently cut and without causing unnecessary damage to the briform. it can.

(12) is a cutting oil spraying device for preventing the preform from being cut poorly due to heat generated when cutting the optical transmission medium (10). (30) is a new blower for pulling out the GI-type optical transmission line of the present invention, and the cutting speed of the preform is the same as the rotation speed of the rotating tooth (22). This can be done by adjusting the take-off speed of the blower (30).

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a diagram showing the refractive index distribution of the optical transmission body of the present invention, Fig. 2 is a diagram showing the refractive index distribution of an optical transmission body developed conventionally, and Fig. 3 is a lattice image observed with the optical transmission body. (A) is a grid image observed using an optical transmission body whose refractive index distribution approximates the quadratic curve defined by equation (3), (b), (b) c) is a lattice image observed using an optical transmitter whose refractive index distribution is farther from the ideal refractive index distribution.

Fig. 4 shows the maximum (i «· χ) and minimum (i min) values of transmitted light using a CCD sensor when observing a lattice image with an optical transmitter.

Figure 5) shows a device for measuring Fig. 6 shows the measurement results of the maximum light quantity and the minimum light quantity, and Fig. 6 shows the outer peripheral cutting device of the optical transmitter preform used to create the optical transmitter of the present invention. FIG. 7 is a diagram showing a refractive index distribution of the optical transmitter of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically with reference to examples. In each of the following examples, the width of each layer of the composite spinning nozzle used was such that the refractive index of the cured product of a plurality of types of uncured liquid material decreased gradually from the center, and the When the refractive index and the thickness of the layer after curing are made into a strand fiber, the center position of each layer is the distance from the center axis to the strand fiber on the horizontal axis. When the refractive index of each layer was plotted on the vertical axis, the one designed to follow the quadratic curve represented by the above equation (2) was used.

Example 1

Polymethylmethacrylate ([TJ] = 0.56, measured at 25 in methylethylketone (MEK)) 46 parts by weight, benzylmethacrylate 44 weight Parts, 10 parts by weight of methyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexylphenolketone and 0.1 parts by weight of hydroquinone are 70 ^e. The mixture was heated and mixed with C to obtain an unhardened liquid material for forming the first layer (center).

Polymethyl methacrylate ([r?] = 0.41, measured at 25 in MEK) 50 parts by weight, methyl methacrylate 50 parts by weight, 1 ー0.2 parts by weight of hydroxy phenyl ketone and 0.1 part by weight of hydroquinone 7 0 and heated mixture to ^e C to the second layer forming uncured liquid substances, Po Li main Chirume data click Re-les over preparative ([rj] = 0. 3 4, MEK during measurement at 2 5 ° C 45 parts by weight, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate 3 5 doube part, methyl methacrylate 20 By weight, 0.2 part by weight of 1-hydroxycyclohexylphenyl ketone and 0.1 part by weight of hydroquinone were heated and mixed at 70 to obtain an uncured liquid material for forming the third layer.

Using a molding machine equipped with a true conjugated type three-layer composite spinning nozzle, the above three types of uncured liquid materials were simultaneously extruded into a strand fiber. Press the viscosity when Shi out material of the first layer 4 5 1 0 -... Boi's, second layer 2 0 X 1 0 ⁴ Boise, third layer 2 2 X 1 0 ⁴ in Boi's there were. The temperature of the composite spinning nozzle was 55 X; Then, after passing 90 cm through the cylinder under a nitrogen atmosphere to perform interdiffusion between the layers, 12 fluorescent lamps of 120 cm in length and 40 W in length are arranged at equal intervals in a circle. A fiber optic with a radius (L.) of 0.5 mm is run at a speed of 50 cmZ at a speed of 50 cmZ so that it passes through the center of the illuminated section. The reform was taken off with a mini-proler. The discharge amount ratio was 1st layer: 2nd layer: 3rd layer = 1: 1: 1: 1. The refractive index distribution was 1.512 at the center (N.) and 1.470 at the periphery, and the refractive index distribution constant (g) was 0.52. 0.25 L from the center to the outer surface as shown in the figure. ~ 0.75 L. The refractive index distribution curve approximating the quadratic curve [I] satisfying the equation (2) in the range of Had.

The end faces of the optical transmitter body were polished to a lens length of 7.2 mm, and the MTF measured using a 4-line Pano mm grid was 57%. Had a conjugate length of 15.4 mm. The image of the obtained lattice was a clear image with little distortion, but distortion was observed in the peripheral part. A plurality of the optical transmitters are assembled into an optical transmitter array having a lens length of 7.1 mm having a structure as shown in FIG. The MTF measured using a 4-line-pair Zmm mm grid of the body array was 49% and the conjugate length was 15.4 mm.

The above-mentioned optical transmission medium was immersed for 45 seconds in a black-hole hologram in which the temperature was kept at 10, and passed through a small hole made in a 1-mm-thick silicone rubber sheet. The portion swollen with the mouth holm (portion F in Fig. 1) was removed to obtain an optical transmitter with a radius (r) of 0.448 mm. As shown by I in FIG. 1, the refractive index distribution of the optical transmission body is 1.512 at the central axis (n.) And 1.474 at the periphery, and the refractive index distribution constant () As shown in the middle of Fig. 1, the value of 0.52 is 0.24r from the central force toward the outer peripheral surface. ~ 0.82 r. Has a refractive index distribution that approximates the quadratic curve I that satisfies Eq. (1).

Both ends of the optical transmission body were polished to a lens length of 7.2 mm, and the MTF measured using a 4-line pair / mm grating was 65%, with a conjugate length of 1.5 mm. It was 4 mm. In addition, the image of the obtained grating is the light before the surface is scraped. It was a clear image with very little distortion including the peripheral part as compared with the transmission body form. .

A plurality of these optical transmitters are assembled into an optical transmitter array having a lens length of 7.2 mm having a structure as shown at 47 in FIG. The MTF measured using a grating with a line pair of Zmm was 56%, and its conjugate length was 15.4. An image scanner was assembled by combining an LED with a light source and a CCD as a light receiving element on this optical transmitter array. This image scanner had a high resolution and was able to transmit clear images. Example 2

The weight of the liquid material for the first layer used in Example 1 in the first layer was 50% by weight of polymethyl methacrylate ([77] = 0.40, measured in MEK at 25). Parts, 20 parts by weight of methyl methacrylate, 30 parts by weight of benzyl methacrylate, 0.2 parts by weight of 1-hydroxycyclohexyl carbonyl ketone and 0.1 part by weight of hydroquinone The mixture obtained by heating and kneading parts by weight at 65 was used as the liquid material for forming the second layer, and the liquid material for the second layer used in Example 1 was used for the third layer. Tactylate ([7?] = 0.40, measured in MEK at 25) 50 parts by weight, methylmethacrylate 30 parts by weight, 2, 2, 3 20 parts by weight of bilmetacrylate, 0.2 part by weight of 1-hydroxycyclohexylphenyl ketone and 0.1 part by weight of hydroquinone The mixture was heated and kneaded in the above to form a liquid material for forming the fourth layer.

A concentric four-layer composite nozzle is made from the above four types of liquid substances. In the same manner as in Example 1, an extruded strand fiber was used at the same time. The viscosity of the Shi pushed out liquid material of the first layer is 4. 5 X 1 0 ⁴ Boi's, liquid material of the second layer is 4.0 1 0 ⁴ Boi's, liquid material of the third layer is 2.0 X 1 0 ", the liquid-like material of the fourth layer is 2. was 2 X 1 0 ⁴ Boi's. temperature of the composite Roh nozzle met 6 0 ^e C.

Next, an optical transmission body foam having a hardening (L.) of 0.48 mm was obtained by curing in the same manner as in Example 1. The optical transmission medium obtained when the discharge ratio is (first layer): (second layer): (third layer): (fourth layer) is set to 2: 1: 1: 1. The refractive index distribution measured with an interface microscope is the central axis (N.

31.5 13, the peripheral part is 1.479, and the refractive index distribution constant (g) is 0.53. From the center to the outer peripheral surface as shown in ΠΙ in FIG. 0.2 L towards you. ~ 0.75 L. The refractive index distribution approximated to the quadratic curve IV shown by the equation (2) in the range of (2). The MTF measured using a 4-line-pair Z mm grid was 5.7% at a lens length of 7.1 mm and a conjugate length of 14.9 mm.

Furthermore, as a result of producing an optical transmitter array in the same manner as in Example 1 by combining a plurality of the optical transmitter preforms, the MTF was 53%.

Dip the above-mentioned optical transmission medium foam into a hologram box for which heat is maintained at 12.5 for 45 seconds, and pass it through a small hole in a lmm-thick silicone rubber sheet. The part swollen with the black hole Holm (G part in Fig. 7) is cut off and the radius (r.

) Was obtained. This optical transmitter The refractive index distribution is 1.512 at the central axis ( _n .) And 1.481 at the periphery, and the refractive index distribution constant (g) is 0.53. 0.19Γ towards you. ~ 0 · 87 r. Has a refractive index distribution approximating the optimal curve satisfying the equation (1).

Both ends of the optical transmission body were polished to a lens length of 7.1 mm, and the MTF measured using a 4-lane Zmm grating was 71%, with a conjugate length of 14.9. mm. In addition, the obtained image of the grating was a clear image with very little distortion including the peripheral part, compared to the optical transmission medium before shaving the surface.

A plurality of these optical transmitters are assembled into an optical transmitter array having a lens length of 7.1 mm and having a structure as shown in FIG. 4 at 47, and the optical transmitter array is assembled into four line pairs. The MTF measured using a lattice of Zmm was 63% at a conjugate length of 14.9. An image scanner was assembled by combining an LED with a light source and a CCD as a light receiving element on this optical transmitter array. This image scanner has a high resolution and was able to transmit clear images. Example 3

Each of the liquid materials for forming the first to fourth layers used in Example 2 and the solution material for forming the fifth layer were used for forming the third layer in Example 1. These liquid materials for each layer are supplied to five layers of concentric composite nozzles, extruded at the same time, made into a strand fiber, cured, and cured to form an optical transmitter preform. I got it. Optical transmitter obtained by setting the discharge ratio to (1st layer): (2nd layer): (3rd layer): (4th layer): (5th layer) = 3: 1: 1: 1: 2 The refractive index distribution of the briform (L .: 0.48 mm) measured by an interferometer interference microscope was 1.514 at the central axis (N.) and around the periphery. Is 1.469, the refractive index distribution constant (g) is 0.57, and 0.15 L from the center toward the outer peripheral surface. ~ 0.79 L. In the range, the refractive index distribution approximated the optimum curve shown by the equation (2). The MTF measured using a 4-line pair Z mm lattice was 5.9% with a lens length of 8.0 mm and a conjugate length of 15.9 mm. Furthermore, the MTF of the optical transmitter array prepared in the same manner as in Example 1 using this optical transmitter preform was 57% (measured with a grid of 4 line pairs / mm). Was.

The optical transmitter preform was removed from the outer peripheral surface using a water-resistant sandpaper (No. 200), and the optical transmitter having a radius (r.) Of 0.44 mm was used. I got The refractive index distribution of this optical transmission body is 1.514 at the central axis ( _n .) And si.4722 at the peripheral portion, and the refractive index distribution constant (g) is 0.57. 0.13 L from center to outer circumference. ~ 0.89 L. The refractive index distribution approximated to the optimal curve represented by the equation (1) in the range of (1). The MTF measured in the same manner as in Example 1 had a lens length of 8.0 mm and a conjugate length of 15.9. It was 75% in mm. Further, the MTF of the optical transmitter array prepared using this optical transmitter in the same manner as in Example 1 was 71% (measured on a 4-line-pair mm grid). Image scanners are not always used, and always transmit high-resolution images. I was able to do it.

Industrial applicability

The GI-type plastic optical transmission body of the present invention has at least 0.25 mm from the center thereof. ~ 0 '8 0 Γ. Since the refractive index distribution in the range of is very similar to the distribution curve shown in equation (1), it is possible to perform high-quality image transmission with no image blur at the periphery and particularly high resolution. It is extremely useful as an optical transmitter for copiers, facsimiles, and LED printers that require a high speed.

Claims

The scope of the claims

Radius. A graded index type plastic optical transmitter having a circular cross-section within a range of 0.45 ± 0.1 mm, and an outer periphery extending from the central axis of the optical transmitter. At least 0.25 r towards the surface. A graded index type plastic characterized in that the refractive index distribution in the range of .about.0.8 r ₀ has a refractive index distribution approximating the refractive index distribution curve defined by the following equation (1). Optical transmission body ο

n (r) = no {1- (g 2/2) r 2} (1)

(In the above formula, n is the refractive index of the central axis of the optical transmission body, and is an arbitrary value within a range of 1.5 ± 0.1, and n (r) is the optical transmission body. The index of refraction at a position at a distance r from the center axis of the optical transmission member to the outer peripheral direction, g indicates the refractive index distribution constant of the optical transmitter, and is a value of 0.3 to 0.7, where r is the value of It indicates the distance from the center axis of the optical transmission body toward the outer periphery.)

> At least 0.25 r from the central axis of the optical transmission body made of plastic to the outer peripheral surface. ~ 0.85 r. The graded index according to claim 1, characterized in that the refractive index distribution in the range (1) has a refractive index distribution approximate to the refractive index distribution curve defined by the above equation (1). Optical transmission body made of brass.

Radius L. A graded index type plastic optical transmitter bliform having a circular cross section in the range of SO.5 ± 0.1 mm, said optical transmitter pref. At least at least from the center axis of the form toward the outer circumference

0.25 L. ~ 0.70 L. Wherein the outer circumference of the optical transmitter preform having a refractive index distribution whose refractive index distribution approximates the refractive index distribution curve defined by the following equation (2) is removed. 4. A method for manufacturing a transmission body made of a gray-index index-type plastic as described in the item (1).

n (L) = no {l- (g 2/2) L 2} (2)

In the above formula, N. Is the refractive index of the central axis of the optical transmission body, is an arbitrary value within the range of 1.5 ± 0.1, and n (L) is the direction from the central axis of the optical transmission body toward the outer periphery. , The refractive index at the position at a distance L to the optical transmission medium, g represents the refractive index distribution constant of the optical transmission medium, and has a value of 0.3 to 0.7, and L is the outer circumference of the optical transmission medium from the central axis. Indicates the distance to the direction. )